In 1991, discussions were held among representatives from NIDA ARC, NIDA DAR, and DOT NHTSA concerning potential collaboration on clinical laboratory studies designed to collect data relevant to NHTSA's Drug Evaluation and Classification (DEC) procedures and, at the same time, allow ARC scientists to investigate behavioral and biological mechanisms underlying the impairing effects of psychoactive drugs on human performance and functioning. After several meetings, it was decided that a series of studies, possibly spanning several years, could be accomplished that would fulfill the missions of both NIDA and DOT. To this end, a first study was designed that will investigate the effects of placebo and two active doses each of alcohol, marijuana, and cocaine on physiological, subjective, and performance indices in human research volunteers. Additionally, law enforcement officials trained in the DEC procedures will attempt to determine what drugs(s), if any, subjects were administered. Plasma drug concentration over time will also be assessed as a biochemical correlate of changes in behavior. Subject testing for this study was begun in June, 1992.